When an existing pipe such as a sewer pipe buried underground has deteriorated, a lining method has been used in which the existing pipe is lined with a pipe lining material. The pipe lining material includes a resin absorbing material that is made of a flexible tubular non-woven fabric having a shape corresponding to that of the existing pipe and is impregnated with an uncured liquid setting resin. The resin absorbing material is coated at its external peripheral surface with a highly airtight plastic film. The pipe lining material is inserted into the existing pipe by means of an eversion or pull-in method. The lining material is pressed against the internal circumferential surface of the existing pipe, and the liquid setting resin is heated and cured to carry out the lining.
Since a lateral pipe communicates with a main pipe such as a sewer pipe, the pipe lining material blocks the opening at the end of the juncture of the lateral pipe when the main pipe is lined with the pipe lining material. Therefore, a work robot provided with a drilling machine and a TV camera is transported into the main pipe and operated remotely from aboveground. The cutter (drilling blade) of the drilling machine is driven and rotated to drill through from the main pipe and remove the portion of the pipe lining material that blocks the lateral pipe opening.
However, in this work, the cutter of the drilling machine must be positioned in the longitudinal direction and in the circumferential direction of the main pipe prior to drilling. This is accomplished while monitoring the main pipe interior with a TV camera. However, since there is no marker in the main pipe interior, there are cases in which mistakes are made in positioning.
As a countermeasure, the following Patent Document 1 discloses a method in which a cap member made of conductive or magnetic material is fitted into a branch opening of the lateral and main pipes, and, after lining the main pip, a portion at which the transition of permittivity or permeability of the cap member becomes maximum is detected as the lateral pipe opening using a detector on the in-pipe work robot to drill a hole in the lateral pipe opening that is blocked by the main pipe lining material.
Patent Document 2 disclose an arrangement in which a magnetism generator is disposed on the lateral pipe side; a magnetic detector is moved along the lined main pipe to detect magnetism from the magnetism generator; and a branch opening of the lateral and main pipes is detected to cut the lining material corresponding to the branch opening.
Patent Document 3 discloses an arrangement in which a marker comprised of a coil and a resonator is embedded coaxially with the pipe axis of the lateral pipe, and, after lining the main-pipe, the marker is magnetically excited by a loop antenna that is provided on a drilling robot. In this arrangement, the marker resonates at a resonance frequency when the loop antenna approaches the branch opening, and a position at which the receiving signal from the resonance signal becomes minimum in level is detected as a center position of the branch opening to perform the drilling work.